Process for the simultaneous desulfurization and conversion of hydrocarbons



PROCESS FOR THE SMULTANEOUS DESULFURIZATION ANDy CONVERSION OF HYDROCARBONS Filed May 19, 1955 June z3, 1959 F' c. woo-D. 2,891,906

PROCESS FOR THE SllVIULTANEOUS DESULFURI- ZATISON AND CONVERSION OF HYDROCAR- BON Frederick C. Wood, Long Beach, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application May 19, 1955, Serial No. 509,523

9 Claims. (Cl. 208-136) This invention relates to an improved process for the conversion of hydrocarbons by contacting them with a granular solid contact material, and particularly relates to an improved process for the simultaneous conversion of relatively low boiling and relatively high boiling hydrocarbon fractions contaminated with hydrocarbon derivatives of sulfur so as to produce in a single operation hydrocarbon fuels for use in internal combustion and gas turbine engines.

Hydrocarbon fractions, usually derived from petroleum and boiling from about 75 F. to as high as 750 F. and higher and including the so-called naphtha and gas-oil fractions, are used to prepare internal combustion engine fuels. These hydrocarbons in their natural state frequently contain excessive and detrimental amounts of hydrocarbon derivatives of sulfur and in some cases these derivatives exist in such great quantities that the sulfur analysis runs as high as by weight. The presence of these compounds is undesirable because of their adverse effect both upon such hydrocarbon refining techniques as catalytic cracking and reforming as well as upon fuel combustion within the internal combustion engine. Various refining techniques have been devised to desulfurize these hydrocarbons so that the gasoline, diesel, and gas turbine engine fuels produced therefrom will not exceed the maximum sulfur specifications. Such refining steps have in the past included sulfuric acid treating, clay treating, contact with catalysts in the presence of hydrogen, and others. Probably the best known and most effective catalytic treatment involves contact of the hydrocarbon with an alumina supported cobalt molybdate catalyst at pressures ranging from about 50 p.s.i.g. to about 2500 p.s.i.g., at temperatures ranging from about 500 F. to about 900 F. at liquid hourly space velocities (LHSV) of from about 0.2 to about 10.0 Volumes of oil per volume of catalst per hour, and in the presence of between about 50 and about 10,000 standard cubic feet (scf.) of recycled hydrogen per barrel of hydrocarbon. In such a process the hydrocarbon derivatives of sulfur are catalytically decomposed and hydrogenated to produce hydrogen sulfide and a saturated hydrocarbon fragment so that the product contains generally less than about 0.01% by weight of sulfur. The liquid yield of this process is often 100% by volume or more. It has been found that this same catalyst can be employed to desulfurize and reform naphtha or gasoline range fractions simultaneously at temperatures between about 750 F. and 1050 F.

In the conventional processes for treating the above described hydrocarbons, the relatively low boiling feed stocks suitable for gasoline manufacture or ordinarily processed separately from the relatively high boiling materials from which fuels for diesel engines and gas turbines are ordinarily prepared. For example the gasolines are refined from materials boiling roughly in the range from 75 F. to about 450 F. while the diesel and from 400 F. to about 750 F.

VUnited States Patent 0 ICE Furthermore these fractions are processed under substantially different pressure and temperature conditions and usually by contacting them with granular contact materials having substantially different properties.

It has now been found that there can be simultaneously produced from the naphtha or low boiling stocks and the gas-oil or high boiling stocks excellent fuels of the premium gasoline and high cetane diesel classes. The process of the present invention achieves this result in a single hydrocarbon contacting column employing a single catalyst under identical pressure conditions and in which similar conditions of temperature and hydrogen gas recycle are employed. The present invention is well adapted to maintain individual control over the simultaneous treatment of naphtha and gas-oil hydrocarbon feed stocks to produce the highest quality gasoline and diesel engine fuels. It permits a substantial reduction in the process equipment required, and actually has been found to realize substantial improvements apparently resulting from an active cooperation of the naphtha and gas-oil processing treatments as hereafter more fully described.

It is therefore a primary object of the present invention to provide an improved hydrocarbon conversion process in the treatment of hydrocarbon fractions containing substantial quantities of hydrocarbon derivatives of sulfur. It is a further object of this invention to produce simultaneously high quality spark ignition, compression ignition, and gas turbine fuels in a single hydrocarbon conversion process.

It is a more specific object of this invention to provide for the simultaneous treatment of naphtha and gas-oil boiling range hydrocarbons in a single reactor and in contact with a single catalyst stream to effect catalytic desulfurization and catalytic aromatization and reforming to produce premium gasoline and diesel fuels.

An additional object of the present invention involves the use of carefully controlled quantities of steam during the catalytic treatment of gas-oil hydrocarbons to reduce by a substantial amount the formation of aromatic hydrocarbons which are undesirable in diesel engine-fuels.

A further object of this invention is to convert catalytically a naphtha hydrocarbon and a gas-oil hydrocarbon simultaneously in separate streams while in the presence of a catalyst of the cobalt molybdate type whereby the contact of each hydrocarbon with the catalyst has been found to exert a beneficial effect upon the other.

Other objects and advantages of the present invention will become apparent to those skilled in the art as the description thereof proceeds.

Brieily the present invention comprises the recirculation of a granular solid contact material, preferably a hydrocarbon conversion catalyst of the cobalt molybdate type, downwardly by gravity as a moving bed through a reaction chamber, then through a catalyst regeneration zone, and then a regenerated catalyst pretreatment zone back into the reaction chamber. Separate hydrocarbon inlets are provided at the top and the bottom of the reaction chamber for the separate introduction of a naphtha or relatively low boiling range hydrocarbon and a gas-oil or relatively high boiling range hydrocarbon feed stock. These hydrocarbons are passed from the ends of the vertical catalyst column through the moving catalyst bed toward an intermediate hydrocarbon product disengaging zone whereby the single reaction chamber is effectively divided into an upper and lower conversion zone. The naphtha hydrocarbon feed is generally derived from petroleum and has a boiling range from as low as F. to as high as about 450 F. The gas-oil hydrocarbon fraction, also generally derived from crude petroleum, has a boiling range from as low as about 400 F. to as high as about 750 F. and possibly somewhat higher. Sulfur contaminated hydrocarbons derived from any other sources, such as from coal carbonization, shale oil retorting, or coal hydrogenation, etc. may also be treated according to the principles of this invention. The two individual hydrocarbon feeds are joined at the intermediate efuent disengaging zone and are removed ,together from the reactor for subsequent treatment as more fully hereinafter described, or they may be removed separately by isolation from each other by a sealing zone into which a seal gas is injected so as to avoid the necessity of distilling the mixed naphtha and gas oil eiuent.

The general conditions under which the process of this invention is effected include operating pressures of from about atmospheric pressure to about 2500 p.s.i.g., temperatures between about 500 F. and about ll00 F., hydrogen recycle rates of from about 50 s.c.f. to about 10,000 s.c.f. per barrel of hydrocarbon feed, and liquid hourly space velocities (LHSV) of from about 0.1 to about volumes of liquid hydrocarbon feed per volume of catalyst in the reaction chamber between the hydrocarbon inlet and the outlet per hour.

The preferred catalyst is cobalt molybdate supported on a silica stabilized activated alumina carrier to which has been added between about 3% and 8% by weight of silica based upon the untreated carrier. The nished catalyst, prepared by any of the impregnation, coprecipitation, or other methods described in the art, contains cobalt and molybdenum impregnated thereon so that the catalyst analyzes between about 7% and about 22% by weight total cobalt oxide and molybdenum trioxide in relative amounts so that the molecular ratio of cobalt oxide (COO) to molybdenum trioxide (M003) is between about 0.4 and about 5.0. Other adsorbent catalyst carriers of the well known types can also be used, however the silica stabilized alumina catalyst carrier is preferred because of its outstanding temperature stability.

In the process of this invention, employing the preferred cobalt molybdate type catalyst indicated above, the higher boiling or gas-oil range hydrocarbon feed is preferably treated for desulfurization in one part of the reaction chamber at a pressure between about 200 p.s.i.g. and about 800 p.s.i.g., at an LHSV of between about 0.5 and 5.0 at a temperature between about 600 F. and about 850 F., and in the presence of between about 2000 s.c.f. and about 8000 s.c.f. of hydrogen per barrel of gas-oil. It -is also preferable to inject, either into the hydrogen stream or into the gas-oil vapor stream entering the reaction chamber, an amount of steam ranging between about 50 and about 1000 s.c.f. per barrel of gasoil. This is approximately equivalent to between about 2.5 and 50 pounds of steam per barrel of oil. The steam may also be separately introduced into the gas-oil conversion zone for passage therethrough with the gas-oil. The presence of these quantities of steam during the gasoil desulfurization has been found to exert no detrimental effect whatsoever upon the degree to which the gasoil is desulfurized and has been found to greatly decrease the dehydrogenation and aromatization of the higher boiling naphthene hydrocarbons in the gas-oil feed stock under the relatively high desulfurization temperatures of 700 F. to 850 F. This result is extremely desirable since the presence of relatively small amounts of aromatic hydrocarbons in diesel fuels markedly lowers the cetane number of the product and reduces by a substantial amount the quantity of saleable diesel fuel obtained.

In the naphtha conversion zone of the reactor chamber, the naphtha hydrocarbon is simultaneously desulfurized and reformed to produce a substantially sulfurfree and high anti-knock rating gasoline by contacting the naphtha with the cobalt molybdate type catalyst at the same operating pressure and at a temperature of between about 800 F. and 1050 F. in the presence of between about 1500 s.c.f. and about 6000 s.c.f. of hydrogen per barrel of naphtha feed, and at an LHSV of between about 0.2 and 1.5 volumes of liquid naphtha per volume of bulk catalyst between the naphtha inlet and the product outlet per hour.

The foregoing reaction conditions are easily maintained and separately controlled in the individual contacting zones of this invention. During gas-oil desulfurization, net exothermic reactions cause the temperature to rise in the direction of the gas-oil conversion zone outlet. Preferably this conversion zone is cooled either indirectly or directly to maintain a substantially isothermal profile. During the naphtha hydrocarbon conversion, particularly when substantial degrees of naphthene dehydrogenation are eifected, the endothermic reactions cause the temperature to decrease in the direction of the naphtha outlet and preferably heat is applied by direct or indirect means to maintain the desired isothermal temperature prole. One form of temperature control in each zone utilizes the injection of recycle hydrogen, either hot or cold, to counteract these temperature changes.

In the process of the present invention it is preferred that the higher boiling or gas-oil hydrocarbon fraction be passed downwardly through the catalyst bed from the top of the reactor toward the product outlet and that the lower boiling or naphtha be passed upwardly from the bottom of the reactor toward the reactor outlet. In this preferred modification it has been found that the gas-oil feed need not be completely vaporized when it is introduced into the reactor thus simplifying feed vaporization. A higher hydrogen concentration may be maintained in the upper or gas-oil desulfurization zone because no naphtha passes therethrough at the same time. The naphtha in the lower portion of the column contacts a partially coked catalyst containing between about 0.25% and about 1.75% by weight of carbon. This catalyst has substantially the same naphtha reforming and desulfurization activity but has been found to have a materially reduced cracking activity so that the naphtha feed is converted to produce a substantially higher liquid yield particularly when the naphtha contains olefin hydrocarbons. This yield increase is often as high as 10% by volume.

The partially deactivated catalyst passing through the lower or naphtha conversion zone is effectively and simultaneously stripped of residual gas-oil by the naphtha and hydrogen at the higher reforming temperatures whereby the usual 10% liquid gas-oil treating loss is eliminated. The net production of hydrogen obtained during naphtha reforming is separated from the combined hydrocarbon product and is recirculated into both the gas-oil and naphtha conversion zones so as to provide for the net consumption of hydrogen in the gasoil desulfurization zone. A separate control over the amount and concentration of hydrogen during the gas-oil and naphtha conversions may be maintained under conditions wherein changing the quantity or concentration of hydrogen in one zone has no effect upon the quantity and concentration of hydrogen in the other zone. The foregoing and other advantages are characteristic of the modification of this invention in which the gas-oil and hydrogen pass concurrently with the fresh cobalt molybdate catalyst downwardly through the upper portion of the reactor and the naphtha and hydrogen pass upwardly countercurrently to the partially deactivated catalyst in the lower part of the reactor.

In another modication of this invention, the gas-oil and hydrogen are introduced at the bottom and naphtha and hydrogen are introduced at the top of the reactor for passage through the lower and upper portions respectively toward the intermediate product outlet in the reverse order from that described above. Although this is a less preferred modication because the gas-oil feed must be fully vaporized, some of the foregoing advantages nevertheless result. Certain new advantages are obtained in this modification such as the use of slightly lower reforming temperatures because the naphtha contacts Ifresh catalyst in the upper conversion zone.

The present invention and the preferred form of apparatus fin which it is readily carried out will be more clearly understood with reference to the accompanying drawing which illustrates an elevation view in partial cross section of the apparatus employed and a schematic flow diagram of the process of this invention.

Referring now more particularly to the drawing, the description of which will be conducted by way of a sp'ecic example of the application of the process of this invention to the simultaneous conversion of a gas-oil and a naphtha hydrocarbon ina semi-commercial size pilot plant, the 'apparatus consists essentially of regenerated catalyst receiving chamber 10, reactor column 12, spent catalyst pressuring chamber 14, and catalyst induction chamber 16. A vertically disposed and elongated conveyance-regenerator conduit 18 communicates at its inlet opening 20 at a low point within induction chamber 16 and at its outlet opening 22 with a high point in regenerated catalyst receiving chamber 10 thus completing the catalyst cycle. The reactor chamber contains at successively lower levels therein lirst recycle gas engaging zone 24, lirst feed engaging Zone 26, upper conversion Zone 28, combined ellluent disengaging zone 30, lower conversion Zone 32, second feed engaging zone 34, spent catalyst stripping zone 36, second recycle gas engaging zone 38 which `is disposed adjacent to catalyst ow rate and distribution control zone 40, and lower hopper zone 42. The cobalt molybdate catalyst passes downwardly as a moving bed by gravity through the aforementioned zones in reactor 12. The-catalyst circulation rate and the flow distribution throughout the cross sectional area of the reactor are controlled by the rate of reciprocation of reciprocable tray 44 Iin catalyst feeder zone 40.

In the present example the preferred modiJication was employed in which first upper conversion zone 28 comprised a gas-oil desulfurization zone. The gas-oil feed was introduced at a rate of l barrels per day through first feed engaging zone 26. Lower conversion zone 32 vwas operated as a combined desulfurization and reform- Ying zone to treat a sulfur contaminated naphtha passed upwardly therethrough at a rate of 20 barrels per day from secondy feed engaging zone 34. 'Ihese ,two hydrocarbon feed stocks had the following properties:

TABLE I Feed stock inspection The gas-oil hydrocarbon is introduced through line 50 at a rate of l0 barrels per day controlled by valve 52 and passed through fired heater and vaporizer 54. The gas-oil vapor then passes at a temperature of 750 F. and a pressure of about 405 p.s.i.g. through line 56 into engaging zone 26 wherefrom it passes downwardly concurrently with the downwardly moving catalyst in desulfurization zone 28. A stream of hydrogen ilows through line 58 at a rate of 5000 s.c.f. per barrel of gasoil controlled by valve 60 and is heated in tired heater 54. This hydrogen then passes `at a temperature of about 750 F. through line l62 into iirst recycle gas engaging zone 24. The major portion of this recycle gas passes downwardly through the catalyst into admixt-ure with the gas-oil vapor and passes downwardly through gas-oil desulfurization zone 28. In an especially preferred modiication of the present invention, relatively low concentrations of steam are maintained in the ud passing downwardly through zone 28 by introducing water` or steam through line 64 at a rate of 40 pounds of steam per ybarrel of oil controlled by valve 66 into first preheater 54. The superheated steam then ilows through line 68 through either valve 70 or 72 into the top# of reactor 12 for downward passage with the hydrogen and gas-oil vapor. It has been found that the use of as little as 50 s.c.f. of steam per `barrel (equivalent to 2.5 pounds of steam per barrel) of gas-oil electively reduces gasoil aromatization reactions during high temperature desulfurization and substantially increases the liquid yield of saleable diesel fuel, but lower amounts appear to be ineffective.

The naphtha hydrocarbon described above is introduced through line 74 at a rate of 20 barrels per day controlled by valve 76 and is passed through second fired preheater 78. The naphtha Vapor at a temperature of about 900 F. and a pressure of about 405 p.s.i.g. `llows through line 80 into and through second feed engaging zone 34, and upwardly through lower conversion zone 32 countercurrently to the downwardly moving partially spent catalyst therein. A hydrogen recycle gas passes through line 82 at a rate of from 3000 to 4000 s.c.f. per barrel of naphtha controlled by valve 84 into and through fired heater 78. The heated hydrogen then passes through line 86 into second recycle gas engaging zone 38, passes upwardly through spent catalyst stripping Zone 36 wherein residual naphtha hydrocarbons are stripped from Ithe spent catalyst, land into and upwardly through lower conversion zone 32 in admixture with the naphtha vapor.

The downwardly moving stream of converted gas-oil vapor, hydrogen, and steam enters eflluent disengaging zone 30 and is therein mixed with the upwardly flowing converted naphtha vapor and hydrogen. The combined effluent is removed through line 83 at a pressure of about 400 p.s.i.g., is cooled and partially condensed in eflluent cooler 90, and is then introduced directly into product fractionation column 92. As noted before, this distillation can be avoided by provision of two disengaging zones like zone 30 separated by a seal gas engaging zone and by removal of two separate eflluents. Herein the reformed and desulfurized naphtha product is distilled from the desulfurzed gas-oil product. 'Ihe overhead vapor flows through line 94, is partially condensed in condenser 96, and the mixture is discharged into vapor liquid separator 98. The uncondensed portion consists essentially of hydrogen recycle gas contaminated with variable amounts of hydrogen sulfide and the lower molecular weight hydrocarbon gases. If desired any net production of gas may be bled from the system through lines and 102 controlled by back pressure regulated valve 104. The remaining gas may then be passed through purification zone 106 in which hydrogen enrichment and hydrogen sulde removal is effected by any of the conventional procedures such as selective adsorption, oil absorption, or solvent extraction. 'The hydrogen rich gas remaining constitutes the recycle gas referred to above and it is pumped through line 108 and recycle gas compressor 110 at a rate of about 130,000 s.ic.f. per day controlled by valve 112 and flow recorder controller 114. This gas flows through line 116, a portion thereof is employed as the lirst recycle gas passing through line 58, another portion constitutes the second recycle gas flowing through line 82, and a third and minor portion is passed through line controlled by valve 122 into regenerated catalyst receiving and pretreating chamber 10.

Referring now to the separator 98, the gasoline condensate is removed therefrom through line 124 and a portion thereof is employed as reliux in column92. The reflux flows through line 126 at a rate controlled by valve 128 and ilow recorder controller 130. The remainder passes through line 132 at a rate controlled by valve 134i and liquid level controller 136 to further process facilities or storage not shown as the gasoline product of this process, The desulfurized gas-oil product is removed from the bottom of column 92 through line 13S at a rate controlled by valve 140 and liquid level controller 142. A portion of this gas-oil product is passed through reboiler 144 and the reheated gas-oil is discharged through line 146 supplying heat to the bottom of distillation column 92.

The physical properties of the gasoline and diesel fuel products from the process of this invention are as follows:

TABLE Il Products inspection Gasoline Boiling Range, F

The naphtha product was produced at a rate of 19.2 barrels per day corresponding to a liquid Volume yield of 96% and the diesel fuel was produced at a rate of 10.1 barrels per day corresponding to a volumetric liquid yield of 101%. The same operation repeated with less than 2.5 pounds of steam per barrel of gas-oil produced a diesel fraction containing 7.5% of aromatics. The use of more than about 50 pounds of steam per barrel of gasoil under the same conditions produced a diesel containing increasing amounts of sulfur, i.e. over 0.50%.

In another experimental run in which a gas-oil heavily contaminated with sulfur was treated according to this invention, the feed stock inspection was as follows:

TABLE III These feed stocks were fed to the pilot plant at barrels per day for the gas-oil and 20 barrels per day for the naphtha. The average reaction zone temperatures were 910 F. for the naphtha and 700 F. for the coker gas-oil. Steam in an amount corresponding to 30 pounds per barrel of gas-oil was added. Hydrogen recycle rates of 3750 scf. per barrel of naphtha and 5500 s.c.f. per barrel of Coker gas-oil were maintained. The gasoline and diesel product fractions had the following properties:

TABLE 1V Products inspection Gasoline Diesel Boiling Range, F 100-420 400-674 Gravity, API 50.6 26.9 Sulfur, Weight Percent 0. 01 0. 46 Nitrogen, Weight Percent. 0.001 0. 08 Knock Rating (F-1-i-3 ce.) 95 Catane Number 36.7 Naphthenes, Volume Percent 7 Aromatics, Volume Percent 50 Acid Solubility, Volume Percent 50 8. 0

Termination of steam injection in the gas-oil desulfurization Zone caused an increase in the acid solubility of the diesel product to a value of 12% and a reduction in cetane value.

The spent cobalt molybdate catalyst following the above described and illustrated treatment is deactivated due to the accumulation thereon of catalytic coke in an amount which usually does not exceed 5% by weight. Although this spent catalyst may be regenerated by conveying it to a separate regeneration chamber wherein the coke is burned to produce a regenerated catalyst and then reconveying this catalyst to the reactor, the preferred structure and process for catalyst regeneration is shown in the accompanying drawing. The spent catalyst is withdrawn from the bottom of reactor 12 through line provided with Valve 152 at a pressure of about 405 p.s.i.g. With a mass 154 of spent catalyst in pressuring chamber 14, valve 152 is closed, valve 156 is opened, and a suicient quantity of spent regeneration gas is injected from lines 158 and manifold 160 to increase the pressure in chamber 14 to a value about 450 p.s.i.g. This increase is substantially equal to the pressure differential existing between inlet opening 20 and outlet opening 22 of conveyance regenerator conduit 18. Valve 156 is then closed, valve 162 is opened, and the pressured spent catalyst gravitates through line 164 into a mass of catalyst 166 in induction chamber 16. Valve 162 is then closed, valve 168 is then opened whereby a portion of the gas is discharged through manifold and line 170 from chamber 14 to return its pressure to a value of about 405 p.s.i.g. Valve 152 is then reopened to admit additional spent solids and the cycle is repeated in sequence controlled by cycle timer operator 172. The rate of solids pressuring is controlled so that it is equal to the rate of solids ow controlled by Zone d0 previously described.

A lower seal gas stream consisting of a mixture of solids pressuring gas and second recycle gas is removed from lower seal gas disengaging zone 174 through line 176 controlled by valve 173 to seal the solids outlet conduit 150 at the bottom of reactor 12.

The downwardly moving mass 166 of spent catalyst submerges inlet 20 of the conveyance regeneration conduit. The spent catalyst is conveyed upwardly therethrough as a dense compact granular mass concurrent with a ow of regeneration-conveyance uid containing oxygen to effect spent catalyst regeneration. The conveyance regeneration gas rate is controlled at a Value suicient to generate a pressure gradient at all points along the length of conduit 18 which satisfies the following equation:

f1-Il 2p@ Gos 0 (1) wherein l@ dl is the pressure gradient in pounds per square foot per foot at any point in the conveyance conduit, p8 is the static bulk density of the spent catalyst in pounds per cubic foot, and 0 is the angular deviation of the conveyance direction from a vertical upward reference axis. When the pressure gradient exceeds a value defined by ,aS cos 0 by an amount sucient to overcome frictional forces acting on the solids, the granular catalyst in the conveyance-regenerator moves upwardly therethrough in a dense nonsuspended form so long as catalyst is provided to inlet 20 and withdrawn from outlet 22. To prevent fluidization and to maintain the dense form of the catalyst, the solids are discharged upwardly against bale which serves to restrict the solids flow but not to restrict the gas discharged from outlet 22.

Catalyst passes downwardly by gravity as a moving bed 182 past upper seal gas disengaging zone 184i downwardly through sealing leg 168 into the top of reactor @seneca 12. A minor portion of hydrogen is introduced through line 120.into upper seal gas engaging zone 186 and passes downwardly therethrough at least partly into the lower opening of sealing leg 188. The hydrogen passes countercurrent to the downwardly moving regenerated catalyst, reduces it preparatory ltoits introduction into reactor 12, and is then disengagedfrom the catalyst in disengaging zone 184. A minor portion of the spent conveyance-regenerationV uid passes downwardly from outlet 22 into disengaging zone 184 and mixes therein with the hydrogen. Thisupper Yseal gas mixture is removed through line 190 at a rateVV controlled by valve 192 and differential pressure recorder controller 194. This maintains atv all Y'times upward ow of seal hydrogen through 'sealing leg 188 to pretreat the catalyst and simultaneously seals the catalyst inlet to reactor 12.

'Ihe major portion of spent conveyance regeneration gas is disengaged from the regenerated catalyst in upper disengaging zone 196 at a temperature of about 1050 F. and passes through line 198 into catalyst lines separator 200. A portion of the lines free spent gas amounting to the net production of flue gas is discharged through line 202 controlled by valve 204 to the atmosphere. The remaining portion is recirculated through line 206 through regeneration gas cooler 208 wherein the ternperature is decreased to about 650 F. The heat is recovered in preheating either one or both of the hydrocarbon feeds, or the recycle hydrogen, or all of them. It is in this cooling means that the liberated heat of regeneration is dissipated after being absorbed in the regeneration conduit 18 as sensible heat in the regeneration gas recycle. The cooled spent regeneration gas passes through line 210, is compressed from about 400 p.s.i.g. to a pressure of about 455 p.s.i.g. in recycle gas compressor 212 and flows through lines 214 controlled by valve 216 and ow recorder controller 218 and through lines 220 and 222 into recycle gas preheatng conduit 224 which surrounds the lower portion of regenerator 18. An oxygen containing gas such as air is introduced through line 226 and is compressed in compressor 228 to about 455 p.s.i.g. also. It then passes through line 230 into line 222 at a rate controlled by valve 232 in accordance with oxygen recorder controller '234, so that a predetermined concentration of oxygen such as between about 0.5 and about 5.0% by Volume is maintained in the fresh regeneration gas entering preheater 224. The gas mixture passes downwardly through annulus 236, is preheated there indirectly by part of the liberated heat of regeneration in the lower part of conduit 18, passes downwardly into inlet opening 20, and upwardly through conduit 18 to convey and regenerate the spent catalyst as described.

In the event that the second modification of this invention is employed as described briefly above, that is, with gas-oil flowing upwardly through the lower conversion zone, the preferred steam introduction to repress aromatic formation is effected by passing water or steam through line 240 at a rate controlled by Valve 242 through tired heater 78 and then either through valves 244 or 246 into the bottom of lower conversion zone 32. This induction is analogous to that performed in the preferred modification at the top of the reactor.

The present invention as described above in considerable detail has been found to be remarkably effective in simultaneously treating the low boiling hydrocarbon naphtha and the relatively high boiling gas-oil hydrocarbon to achieve remarkably high liquid yields of substantially improved products suitable for direct use as fuels. These improved yields and qualities are directly attributable to the simultaneous contacting of the naphtha and the gas-oil with a cobalt molybdate catalyst in a single reactor and the active cooperation between the two contact steps as described above. The substantial absence of aromatic hydrocarbons from the gas-oil fraction compared to the exceedingly high concentration of aromatic 10 hydrocarbons in the naphtha fraction of the product is obtained by the use of small controlled quantities of steam in the gas-oil conversion.

A particular embodiment of the present invention has been hereinabove described in considerable detail by way of illustration. It should be understood that various other modifications and adaptations thereof may be made by those skilled in this particular art without departing from the spirit and scope of this invention as set forth in the appendedvclaims.

I claim: l

1. In a method for the simultaneous desulfu-rization and aromatization `of a naphtha boiling range hydrocarbon contaminated with hydrocarbon derivatives of sulfur which comprises contacting said hydrocarbon at a temperature between about 800 F. and about `1050 F.` and a pressure between about 50 p.s.i.g. and about 2500 p.s.i.g. with a cobalt molybdate catalyst analyzing between about 7% and about 22% by weight total CoO plus M003, wherein the molecular ratio of CoO to M003 is between about 0.4 and about 5.0, in the presence of between about 50 s.c.f. and 10,000 s.c.f. of hydrogen per barrel of hydrocarbon, the improvement in substantially eliminating the simultaneous loss of hydrocarbon and undesirably rapid deactivation of said cobalt molybdate catalyst due to cracking by the step of first contacting said catalyst with a mixture of gas oil, steam and hydrogen at a temperature between about 600 F. and about 850 F. to produce a desulfurized gas oil product and a partially deactivated cobalt molybdate catalyst containing residual quantities of gas oil, and then using said catalyst to desulfurize and aromatize said naphtha, said steam being employed in amounts ranging between about 2.5 and 50 pounds per barrel of said gas oil.

2. A method according to claim l wherein the preliminary gas oil desulfurization is conducted to produce said p-artially deactivated catalyst analyzing between about 0.25% and about 1.75% by weight of carbon.

3. An improved process for the upgrading of hydrocarbons contaminated with organic sulfur compounds, which comprises circulating a bed of cobalt molybdate catalyst serially through an upper gas oil treating zone, a lower naphtha treating zone, a catalyst regeneration zone and back into said gas oil treating zone, concurrently contacting the regenerated catalyst in said gas oil treating zone with a mixture made up of (l) gas oil, (2) from 2000 to 8000 s.c.ff. of hydrogen per barrel of gas oil, and (3) 2.5 to 50 pounds of steam per barrel of gas oil, maintaining therein a temperature of about 600 to 850 P. to produce a desulfurized diesel fuel stock of low aromaticity and a partially deactivated catalyst, countercurrently contacting the partially deactivated catalyst in said naphtha treating zone with a mixture of naphtha and from 1500 to 6000 s.c.f. of hydrogen per barrel of naphtha, maintaining therein a temperature of from 800 to 1050 F. to strip residual gas oil from said catalyst and to produce a desulfurized gasoline stock of increased aromaticity and a spent catalyst, and removing said desulfurized diesel fuel stock and said gasoline stock at an intermediate point between said gas oil treating zone and said naphtha treating zone.

4. A process as defined in claim 3 in combination with the step of maintaining said naphtha and gas oil treating zones at substantially equal pressures between about 200 and 800 p.s.i.g.

5. A process as defined in claim 3 wherein said spent catalyst is subjected to regeneration with an oxygen containing gas and reduction with a hydrogen containing gas and is then recirculated to said gas oil treating zone.

6. A process as defined in claim 3 wherein said catalyst contains between about 7% and 22% by weight of cobalt oxide plus molybdenum oxide, and wherein the molecular ratio of CoO to M003 is between about 0.4 and 5.0, the balance of said catalyst consisting essentially of activated alumina.

itil

7. A method for the manufacture of high quality diesel fuel from a low grade gas oil contaminated with organic sulfur compounds which comprises contacting said gas oil at a pressure between about 200 and 800 p.s.i.g., a ternperature between about 600 and 850 F., and a space velocity between about 0.5 and 5.0 with a cobalt molybdate catalyst analyzing between about 7% and 22% by weight of total CoO plus M003, wherein the molecular ratio of CoO to M003 is between about 0.4 and 5.0, iu the presence of (l) between about 2000 and 8000 s.c.f. of hydrogen per barrel of gas oil and (2) between about 2.5 and 50 pounds of steam per barrel of gas oil, and recovering high quality diesel fuel from said contacting.

8. A process as dened in claim 7 wherein said cobalt molybdate component is supported on a carrier which is 15 2,753,059

predominantly activated alumina.

E2 9. A process asjdened in claim,7 wherein said cobalt molybdate component is supported ona cam'er consisting essentially of an activated, co-precipitated gel of alumina with a minor proportion oisilica.

References Cited in the le of this patent UNITED STATES PATENTS 2,171,009 RostinA et a1 Aug. 29, 1939 2,293,759 Penisten Aug. 25, 1942 2,356,611 Peters Aug. 22, 1944 2,418,673 Sinclair Apr. 8, 1947 2,428,532 Schulze. et al. Oct. 7, 1947 Berg Aug. 7, 1956 

7. A METHOD FOR THE MANUFACTURE OF HIGH QUALITY DIESEL FUEL FROM A LOW GRADE GAS OIL CONTAMINATED WITH ORGANIC SULFUR COMPOUNDS WHICH COMPRISES CONTACTING SAID GAS OIL AT A PRESSURE BETWEEN ABOUT 200 AND 800 P.S.I.G., A TEMVELOCITY BETWEEN ABOUT 0.5 AND 5.0 WITH A COBALT MOLYBDATE CATALYST ANALYZING BETWEEN ABOUT 7% AND 22% BY WEIGHT OF TOTAL CO0 PLUS MO03, WHEREIN THE MOLECULAR RATIO OF CO0 TO MO03 IS BETWEEN ABOUT 0.4 AND 5.0, IN THE PRESENCE OF (1) BETWEEN ABOUT 2000 AND 8000 S.C.F. OF HYDROGEN PER BARREL OF GAS OIL AND (2) BETWEEN ABOUT 2.5 AND 50 POUNDS OF STEAM PER BARREL OF GAS OIL, AND RECOVERING HIGH QUALITY DIESEL FUEL FROM SAID CONTACTING
 8. A PROCESS AS DEFINED IN CLAIM 7 WHEREIN SAID COLBALT MOLYBDATE COMPONENT IS SUPPORTED ON A CARRIER WHICH IS PERDOMINANTLY ACTIVATED ALUMINA. 